drm/radeon/kms: fix DP training for DPEncoderService revision bigger than 1.1

drm/radeon/kms: fix DP training for DPEncoderService revision bigger than 1.1

commit 5a96a899bbdee86024ab9ea6d02b9e242faacbed upstream.

DPEncoderService newer than 1.1 can't properly program the DP (display port)
link training. When facing such version use the DIGxEncoderControl method
instead. Fix DP link training on some R7XX.

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>